EUMeTrain: Passage of intense cold front/convective line over Europe, 29 February to 01 March 2008

Authors

DWD
Wilfried Jacobs

ZAMG
Jarno Schipper

KNMI
Rob Groenland

Introduction

The storm "Emma" was the only storm that influenced bigger parts of Europe since Kyrill (18-19 January 2007). In Germany at least 4 people were killed and many injured (from N24-News, http://www.n24.de/news/newsitem_431527.html). On 29th February 2008, 00 UTC, Emma's position was south of Iceland. During the next 24 hours it intensified and arrived at the west coast of Norway (surface weather chart from 01st March 2008, 00 UTC ). In the lee of the Norwegian mountains a second centre developed which can be found south of Oslo in the surface weather chart of (surface weather chart from 01st March 2008, 06 UTC). Only during 6 hours the cold front moved from the German coast to Middle Germany. The cold front's passage reveals a strong temperature decrease of about 10 K (12°C to 2°C, (meteogram from Stuttgart, source: http://www.wetter-express.de/Artikel/Emma/emma01.htm, Marco Puckert, 03rd March 2008). During the next few hours the temperature increased again.

Many thunderstorms, graupel/hail were observed and severe (gusts were measured, e.g., Saarbrücken (Saarland, 65 kn), Chemnitz (Saxonia, 83 kn), Ansbach and Mühldorf (Bavaria, 72 kn and 75 kn, respectively). Also in Austria heavy gusts were registered, e.g., Salzburg and Vienna 77 kn. In the Netherlands (without Islands) gusts of up to 60 kn happened. Several tornados developed (2 F1-tornados and 28 (suspicion) over Germany, (more: www.tornadoliste.de, in German). In Austria, expecially in the so-called "Salzkammergut" severe damages happened that fits well to the F2-level (taken from Felix Welzenbach, www.wetteran.de/analysen/emma-und-fee.html, in German).

Damages near Zwickau (taken from "Feuerwehr Meerane") Gusts pushed a bus off the slippery road (Photo: DPA)

The left image shows (below) the cold front and the clouds with embedded convection near the succeeding trough's axis. The right image reveals the airmass composite and the lightning detection during the last hour (green: 7:00 to 7:10 UTC, red: 7:50 to 8:00 UTC). We see the fast movement of the convective line (about 100 km/h).
Meteosat-8 RGB HRV/HRV/IR10.8 (01 March 2008, 08 UTC) Meteosat RGB "Airmass" and lightning detection (last hour) (01 March 2008, 08 UTC)

This case study deals with different parameters describing development stages of cyclones. After the passage of the cold front partly heavy thunderstorms with hail developed near the trough's axis. Heavy gusts occurred. We will investigate


Parameters used in this case study:

Preconditions likely for thunderstorms: When upward motion occurs severe convection can start in a potentially unstable airmass. A potentially unstable airmass is normally characterized by relatively warm and moist air in lower levels of the atmosphere and relatively cold and dry air aloft.


Cylogenesis and storm development:

The following conditions should be checked

We will discuss these phenomena with several basic meteorological parameters and derived model parameters in relation to Meteosat images. Radar data and lightning detection will be additionally used.


Following conceptual models are considered: